Running Lazarus 1.6.2, FPC 3.0.0, when compiling latest OPM from SVN, I get the following error:
Compile package OnlinePackageManager 1.0: Exit code 1, Errors: 1
opkman_mainfrm.pas(39,16) Fatal: Cannot find PackageLinkIntf used by opkman_mainfrm of package OnlinePackageManager.