Who said anything about having to pay to use the site?
Only the ROM section is password protected, and this was done because ROM downloads took up a disproportionate amount of the site's bandwidth. The decision was taken to limit ROM downloads to those who actually contributed something to SMS Power! (for example, sending a cartridge to dump, or making a small donation).
Those who just want the ROMs can use one of the many available mirror sites - there's absolutely nothing in the password protected area of the site that isn't duplicated elsewhere. The only difference is that you'll be using someone else's bandwidth and not SMS Power's.
Incidentally SMS Power! celebrates its fifth anniversary in 2 days time, and has contributed more than 380 ROMs (and countless re-dumps) to the SMS community in that period. This couldn't have been done without the contributions that you say aren't worthwhile