1) Independently of whether a contract exists, the developer owns the IP. By failing to pay at the agreed-upon time, (possibly even before that if you have a good lawyer) the entrepreneur is in material breach of any verbal contract that existed and in a material breach situation the developer has no obligation to "perform" (transfer the IP). The developer is of course entitled to a legal remedy, that does not mean he is obligated to seek one--he has apparently chosen the remedy of open-sourcing the software.
2) Absent an in-force contract (see #1), the status of the copyright falls to statute, which says that if no money changed hands (and sometimes even if money changed hands), the developer retains the copyright.
3) Defamation in the US requires the plaintiff to prove the defendant's "actual malice". If the developer is spouting a legal theory that he in fact believes to be true, a belief that would survive a preliminary hearing, he's not being malicious. Lawyers don't get defamation lawsuits for advocating a legal theory. He is probably wise not to name the entrepreneur to avoid a lawsuit, but that does not mean he would be by necessity a libeler.
1) Independently of whether a contract exists, the developer owns the IP. By failing to pay at the agreed-upon time, (possibly even before that if you have a good lawyer) the entrepreneur is in material breach of any verbal contract that existed and in a material breach situation the developer has no obligation to "perform" (transfer the IP). The developer is of course entitled to a legal remedy, that does not mean he is obligated to seek one--he has apparently chosen the remedy of open-sourcing the software.
2) Absent an in-force contract (see #1), the status of the copyright falls to statute, which says that if no money changed hands (and sometimes even if money changed hands), the developer retains the copyright.
3) Defamation in the US requires the plaintiff to prove the defendant's "actual malice". If the developer is spouting a legal theory that he in fact believes to be true, a belief that would survive a preliminary hearing, he's not being malicious. Lawyers don't get defamation lawsuits for advocating a legal theory. He is probably wise not to name the entrepreneur to avoid a lawsuit, but that does not mean he would be by necessity a libeler.