> there is bzip2 by default without installing external client. If you do XADLibInfo you get:
> BZip2 | 5045 | 13 | 1.9 | FILE,FREE(FI)

Yes, see there:
https://morph.zone/modules/newbb_plus/viewtopic.php?forum=3&topic_id=9556&start=79

:-)

> I can't see it as any external file anywhere, so I guess some of those clients come with
> xadmaster.library itself?

Exactly. You can recognize the external clients by the keyword "EXTERN" in the list generated by xadlibinfo. All other ones are internal to xadmaster.library.