There is a defect in how BoneCP/Heroku/Play deal with connections. I made a fix to BoneCP on github under:
https://github.com/wwadge/bonecp/pull/10
Also, the compiled library is available by adding the following to Build.scala:
val appDependencies = Seq(
"com.jolbox" % "bonecp" % "0.8.0-rc2-SNAPSHOT-20130712-14382677.jar",
....
val main = PlayProject(appName, appVersion, appDependencies, mainLang = JAVA).settings(
libraryDependencies += "com.jolbox" % "bonecp" % "0.8.0-rc2-SNAPSHOT-20130712-14382677.jar" from "https://dl.dropboxusercontent.com/u/36714110/libraries/bonecp-patches/bonecp-0.8.0-rc2-SNAPSHOT-20130712-14382677.jar"
,resolvers += ...