What is a license?
It becomes a struggle when trying to deal with a large amount of software with completely different license agreements, some single boxed copies, some multi user agreements about what exactly you have to prove you have a license to use it. Anyone who has taken over another company or got a new role as head of IT will recognise the problems if meticulous paperwork hasn't been stored.
Is it the receipt/invoice, the physical CD, the license agreement envelope, the sales contract, an e-mail conversation, a license certificate, the licensing server, the Help:About screen information?
It becomes even more complicated with OEM software, how much of a PC can you upgrade/replace before the OEM license is not valid. You aren't, for instance, allowed to buy 20 identical PCs with OEM Windows and clone to them a company hard drive image which was made with Windows OEM off one of those machines, or are you?
All of those options have flaws and there is no standard. If software always had a standard certificate or card that explained the terms of the license and how many it was licensed for it could be so much easier. Maybe for SMEs it could be a sticker per PC or a Card per license that gets kept with the PC. Maybe every piece of software should have a licence certificate with the exact details that is stored in a fireproof safe. Maybe there should be an encrypted license file that is sent or downloaded that you install on a standard licensing server which can be set to Audit PCs at a certain interval to make sure concurrency or user count are not exceeded?