[OSI Board of Directors snipped from distribution.]

Quoting Walter van Holst (walter.van.holst@gmail.com):

> It is hard to provide help if you're this thin on the details, especially on
> the terms of the contract under which Ladislave et al provided their
> services. If said contract states that any copyrights arising from their
> work is assigned to the client, the client's lawyers may have a, albeit
> somewhat twisted, point.

In United States jurisdictions, a conveyance of copyright title must be
in writing and signed by the owner (impliedly identifying some extant
property to be conveyed).  I very much doubt that a judge would agree
that a contract saying "Stuff you make for the next N months shall
belong to me" qualifies in that department.  (My opinion; yours for a
small fee and disclaimer of reverse-engineering rights.)

As detailed earlier, such an agreement _can_ be created and enforced 
between contractor and payer, provided that contractor specifically 
agrees to such "work for hire" treatment, but only in a specified,
limited set of fields of endeavour, that do not happen to include
software.

(Sorry, but some contract terms are just not enforceable.  Surprise.)

However, I am not going to make pronouncements about the merits of
Ladislav's particular case, and probably you shouldn't, either.  For
that, he needs to consult good professional legal counsel.