FlexLM is still going "strong" and used to encumber many scientific pieces of software widely used. It's exactly as you describe and incredibly user hostile -- albeit somehow the "best" DRM scheme out of many bad options in a space that often includes hardware dongles like iLok. It's incredibly frustrating to e.g. pay >$1m for a piece of kit and get a DRM encumbered UI for it, deliberately designed to make life awkward.

Of course, the obvious issue with the public key approach listed as being "best" in the article is that all it takes for an attacker to overcome the scheme is to replace your private keys with theirs -- or to patch a JMP for every do_license_check() call in the binary. It's fundamentally an approach that is always hackable.