The Germans refer to them as "free" inventions, but I'm not sure if that would fly for formal US English usage.

If the employer fails to claim the invention within the four-month period, the invention is considered to be free, ie, the invention is the sole property of the employee (but, where applicable, cumbered with the employer’s nonexclusive right to use if the invention was claimed limitedly).

http://www.iam-magazine.com/issues/article.ashx?g=e22454bd-0...

Alle sonstigen Erfindungen von Arbeitnehmern sind freie Erfindungen, die der Arbeitnehmer seinem Arbeitgeber zwar mitteilen und zur nichtausschließlichen Benutzung anbieten muss (§§ 18, 19 ArbnErfG), die er aber im Übrigen selbständig zum Patent anmelden und verwerten kann.
http://www.tu-darmstadt.de/forschen/erfindungenpatentelizenz...

Gebundene Erfindung – tied invention
Freie Erfindung – free invention

http://tinyurl.com/y645mtc


Where that applies, inventions are called service inventions, or tied inventions. If those conditions are not fulfilled, they are free inventions. For free inventions, the inventor is in total command of his patent or utility model. For service inventions, in contrast, the employer has the right to totally or partially claim the patent. In case of a total claim, any proprietary invention rights and duties (the initial costs and fees as well as potential profits) are transferred to the employer. In case of a partial claim, the employer is only entitled to exploit the invention. In both cases, the inventor is entitled to a reimbursement.

http://www.working-in-germany.com/employee-invention-0087.ht...

http://www.wipo.int/clea/en/text_html.jsp?lang=en&id=1004

I see things slightly differently from the others here. In the context of an R&D agreement between a university and a company, I would expect this to refer to the distinction between "free inventions" and "service inventions" (Diensterfindungen) [often referred to as employment or employer inventions in English], and thus to service inventions becoming free inventions, as described in Kim's links, especially the final WIPO reference.

An invention that is free or becomes free is free in the sense that it is owned by the employee and the university or company has no claim on it. These are the rights then to be assigned here. I do not believe that it means free in the sense of free from patent protection, which is what entering the public domain would imply. An invention enters the public domain, meaning that it is free for anyone to use, when its patent protection lapses (usually after 20 years), or if patent protection is never obtained or applied for. Although "gemeinfrei" is used to mean "in the public domain" in this sense, I really don't believe that is what is meant here. The agreement will be designed to ensure that the company paying for the research can patent and exploit the invention.

This link provides useful general information about R&D agreements between German universities, university employees and companies.

The Act contains a specific provision relating to inventions made by professors and assistant professors of universities (usually called ‘privilege’). These inventions were not considered employment inventions but free inventions, that is the professor was entitled to exploit such an invention on his or her own. On the basis of privilege, many companies concluded research and development (R&D) agreements with professors, according to which, among other things, the professor assigned all inventions made under the agreement to the company.
In a first step to amend the Act, privilege was abolished on February 7 2002 so that in future corresponding inventions will be considered employment inventions which may be claimed by the university. For this reason from now on R&D agreements must be concluded with the university or preferably with both the university and the professor to ensure that the company paying for the R&D work can actually acquire all inventions originating from it. If the professor is only made party to the R&D agreement, the university which has the preferential right in such inventions, may refuse to assign them to the company.
http://www.managingip.com/Article/1256177/Germany---Employme...