diff --git a/build.xml b/build.xml
index 5e33415..ff450ff 100644
--- a/build.xml
+++ b/build.xml
@@ -34,6 +34,12 @@
     <condition property="build.torrent">
       <isset property="snark.present"/>
     </condition>
+    <available property="javaws.present"
+     classname="com.sun.javaws.jardiff.JarDiff" classpathref="clazzpath"/>
+    <echo message="Have Java Web Start: ${javaws.present}"/>
+    <condition property="build.differ">
+      <isset property="javaws.present"/>
+    </condition>
   </target>
 
   <!-- prepares the application directories -->
@@ -53,7 +59,7 @@
     <copy todir="${deploy.dir}/lib" flatten="true">
       <fileset refid="${app.name}.libs"/>
     </copy>
-    <copy todir="${deploy.dir}/lib" file="${java.home}/lib/javaws.jar"/>
+    <copy todir="${deploy.dir}/lib" file="${java.home}/lib/javaws.jar" failonerror="false"/>
   </target>
 
   <!-- cleans out the intermediate build files -->
@@ -74,6 +80,7 @@
            classpathref="clazzpath" includeAntRuntime="no"
            source="1.5" target="1.5">
       <exclude name="**/TorrentDownloader*" unless="build.torrent"/>
+      <exclude name="**/tools/Differ*" unless="build.differ"/>
       <compilerarg value="-Xlint:unchecked"/>
     </javac>
   </target>
diff --git a/src/java/com/threerings/getdown/data/Application.java b/src/java/com/threerings/getdown/data/Application.java
index 5c1da21..a37756c 100644
--- a/src/java/com/threerings/getdown/data/Application.java
+++ b/src/java/com/threerings/getdown/data/Application.java
@@ -55,7 +55,7 @@ import com.samskivert.text.MessageUtil;
 import com.samskivert.util.RunAnywhere;
 import com.samskivert.util.StringUtil;
 
-import org.apache.commons.io.CopyUtils;
+import org.apache.commons.io.IOUtils;
 
 import com.threerings.getdown.Log;
 import com.threerings.getdown.util.ConfigUtil;
@@ -878,7 +878,7 @@ public class Application
         try {
             fin = targetURL.openStream();
             fout = new FileOutputStream(target);
-            CopyUtils.copy(fin, fout);
+            IOUtils.copy(fin, fout);
         } finally {
             StreamUtil.close(fin);
             StreamUtil.close(fout);
diff --git a/src/java/com/threerings/getdown/tools/Differ.java b/src/java/com/threerings/getdown/tools/Differ.java
index 8874725..76d5dd8 100644
--- a/src/java/com/threerings/getdown/tools/Differ.java
+++ b/src/java/com/threerings/getdown/tools/Differ.java
@@ -37,7 +37,7 @@ import java.util.zip.ZipEntry;
 import java.security.MessageDigest;
 
 import com.sun.javaws.jardiff.JarDiff;
-import org.apache.commons.io.CopyUtils;
+import org.apache.commons.io.IOUtils;
 
 import com.samskivert.io.StreamUtil;
 
@@ -53,18 +53,6 @@ import com.threerings.getdown.data.Resource;
  */
 public class Differ
 {
-    /** A suffix appended to file names to indicate that a file should be
-     * newly created. */
-    public static final String CREATE = ".create";
-
-    /** A suffix appended to file names to indicate that a file should be
-     * patched. */
-    public static final String PATCH = ".patch";
-
-    /** A suffix appended to file names to indicate that a file should be
-     * deleted. */
-    public static final String DELETE = ".delete";
-
     /**
      * Creates a single patch file that contains the differences between
      * the two specified application directories. The patch file will be
@@ -160,7 +148,7 @@ public class Differ
                         // their entirety before running jardiff on 'em
                         File otemp = rebuildJar(orsrc.getLocal());
                         File temp = rebuildJar(rsrc.getLocal());
-                        jout.putNextEntry(new ZipEntry(rsrc.getPath() + PATCH));
+                        jout.putNextEntry(new ZipEntry(rsrc.getPath() + Patcher.PATCH));
                         jarDiff(otemp, temp, jout);
                         otemp.delete();
                         temp.delete();
@@ -171,7 +159,7 @@ public class Differ
                 if (verbose) {
                     System.out.println("Addition: " + rsrc.getPath());
                 }
-                jout.putNextEntry(new ZipEntry(rsrc.getPath() + CREATE));
+                jout.putNextEntry(new ZipEntry(rsrc.getPath() + Patcher.CREATE));
                 pipe(rsrc.getLocal(), jout);
             }
 
@@ -181,7 +169,7 @@ public class Differ
                 if (verbose) {
                     System.out.println("Removal: " + rsrc.getPath());
                 }
-                jout.putNextEntry(new ZipEntry(rsrc.getPath() + DELETE));
+                jout.putNextEntry(new ZipEntry(rsrc.getPath() + Patcher.DELETE));
             }
 
             StreamUtil.close(jout);
@@ -252,7 +240,7 @@ public class Differ
     {
         FileInputStream fin = null;
         try {
-            CopyUtils.copy(fin = new FileInputStream(file), jout);
+            IOUtils.copy(fin = new FileInputStream(file), jout);
         } finally {
             StreamUtil.close(fin);
         }
diff --git a/src/java/com/threerings/getdown/tools/Patcher.java b/src/java/com/threerings/getdown/tools/Patcher.java
index acdd508..7e06df0 100644
--- a/src/java/com/threerings/getdown/tools/Patcher.java
+++ b/src/java/com/threerings/getdown/tools/Patcher.java
@@ -30,7 +30,7 @@ import java.util.jar.JarFile;
 import java.util.zip.ZipEntry;
 
 import com.samskivert.io.StreamUtil;
-import org.apache.commons.io.CopyUtils;
+import org.apache.commons.io.IOUtils;
 
 import com.threerings.getdown.Log;
 import com.threerings.getdown.util.ProgressObserver;
@@ -43,6 +43,15 @@ import com.threerings.getdown.util.ProgressObserver;
  */
 public class Patcher
 {
+    /** A suffix appended to file names to indicate that a file should be newly created. */
+    public static final String CREATE = ".create";
+
+    /** A suffix appended to file names to indicate that a file should be patched. */
+    public static final String PATCH = ".patch";
+
+    /** A suffix appended to file names to indicate that a file should be deleted. */
+    public static final String DELETE = ".delete";
+
     /**
      * Applies the specified patch file to the application living in the
      * specified application directory. The supplied observer, if
@@ -68,18 +77,18 @@ public class Patcher
             long elength = entry.getCompressedSize();
 
             // depending on the suffix, we do The Right Thing (tm)
-            if (path.endsWith(Differ.CREATE)) {
-                path = strip(path, Differ.CREATE);
+            if (path.endsWith(CREATE)) {
+                path = strip(path, CREATE);
                 System.out.println("Creating " + path + "...");
                 createFile(file, entry, new File(appdir, path));
 
-            } else if (path.endsWith(Differ.PATCH)) {
-                path = strip(path, Differ.PATCH);
+            } else if (path.endsWith(PATCH)) {
+                path = strip(path, PATCH);
                 System.out.println("Patching " + path + "...");
                 patchFile(file, entry, appdir, path);
 
-            } else if (path.endsWith(Differ.DELETE)) {
-                path = strip(path, Differ.DELETE);
+            } else if (path.endsWith(DELETE)) {
+                path = strip(path, DELETE);
                 System.out.println("Removing " + path + "...");
                 File target = new File(appdir, path);
                 if (!target.delete()) {
@@ -152,8 +161,7 @@ public class Patcher
         InputStream in = null;
         FileOutputStream fout = null;
         try {
-            CopyUtils.copy(in = file.getInputStream(entry),
-                           fout = new FileOutputStream(patch));
+            IOUtils.copy(in = file.getInputStream(entry), fout = new FileOutputStream(patch));
             StreamUtil.close(fout);
             fout = null;
 
diff --git a/src/java/com/threerings/getdown/util/LaunchUtil.java b/src/java/com/threerings/getdown/util/LaunchUtil.java
index c95dd93..becfd97 100644
--- a/src/java/com/threerings/getdown/util/LaunchUtil.java
+++ b/src/java/com/threerings/getdown/util/LaunchUtil.java
@@ -25,7 +25,7 @@ import java.io.FileInputStream;
 import java.io.FileOutputStream;
 import java.io.IOException;
 
-import org.apache.commons.io.CopyUtils;
+import org.apache.commons.io.IOUtils;
 
 import com.threerings.getdown.Log;
 
@@ -105,10 +105,9 @@ public class LaunchUtil
             if (newgd.renameTo(curgd)) {
                 oldgd.delete(); // yay!
                 try {
-                    // copy the moved file back to getdown-dop-new.jar so that
-                    // we don't end up downloading another copy next time
-                    CopyUtils.copy(new FileInputStream(curgd),
-                                   new FileOutputStream(newgd));
+                    // copy the moved file back to getdown-dop-new.jar so that we don't end up
+                    // downloading another copy next time
+                    IOUtils.copy(new FileInputStream(curgd), new FileOutputStream(newgd));
                 } catch (IOException e) {
                     Log.warning("Error copying updated Getdown back: " + e);
                 }
@@ -125,8 +124,7 @@ public class LaunchUtil
         // that didn't work, let's try copying it
         Log.info("Attempting to upgrade by copying over " + curgd + "...");
         try {
-            CopyUtils.copy(new FileInputStream(newgd),
-                           new FileOutputStream(curgd));
+            IOUtils.copy(new FileInputStream(newgd), new FileOutputStream(curgd));
         } catch (IOException ioe) {
             Log.warning("Mayday! Brute force copy method also failed.");
             Log.logStackTrace(ioe);