> I'm not certain GNU parallel's approach to obtaining funding is a good strategy,
Indeed, it's a good question! I know that, for the SGI UV300 we got through an NIH S10 grant, the usage of the supercomputer is tracked by looking for the grant number in publication acknowledgements. Yes, we already got the money, so you may wonder "what does it matter?", but our ability to get future funding (especially as the UV300 nears retirement age) depends (at least in part) on showing how well we used our previous funding.
In our case, the funding came through an NIH grant, so we ask people reference the grant number. But more broadly, and especially for software, issuing a DOI for released versions (through a service like Zenodo https://zenodo.org), along with a request for acknowledgement, gives a way to track usage. For example, the 20150322 release of parallel (DOI 10.5281/zenodo.16303) has been cited at least 63 times (per https://doi.org/10.5281/zenodo.16303).
Looking at https://scholar.google.com/citations?user=D7I0K34AAAAJ&hl=en, it seems the 2011 version of Parallel has been cited over 1,000 times.
The author is at the University of Copenhagen (per the Google Scholar link above), so it's entirely possible that at least some of the funding for his employment is coming from sources that use citation counts as an indicator that they are "getting their money's worth" by continuing to fund (at least part of) Mr. Tange's employment.