I cloned the JPPack, and can confirm that it does not compile with Laz trunk / FPC 3.0.4. OK - the author requires FPC 3.3.1 (it is a bad idea to tie a package of general interest to the latest FPC version).
The main problem, however, is that the package depends also on "JPLib", another library of routines of the same author. It can be found on the author's github site but there is no Lazarus package. Since these libraries are actively maintained by their author it does not make sense that somebody of the Lazarus team takes responsibility to make them available in OPM.
Alextp, if you are interested in having these components available get in touch with their author and ask him to follow the Lazarus standards (i.e., provide a package, no pollution of search path as in Delphi). I am sure the FPC version issue can be handled by a few "IF FPC_FullVersion" checks I would say: minimum requirement is the current FPC release version.