You are right, you should not apply for a membership if you only want to download one schematic.
With some time investment you probably find most schematics for free somewhere.
To get a membership is not a rapid and easy process. Radiomuseum.org tries to get better quality by having real names and addresses instead of anonymous users and it likes members who do help to build up from what you take advantage of: a most complete reference work for radios and related ... "Naturally" more than 50 % have never shown any activity (uploading) but that is normal.
To get the ability for all what is possible in Radiomuseum, this means that in my house I pay a full time programmer since years - at the moment it is one plus one software engineer for 50% of time. Radiomuseum implies a lot of traffic (daily 20 thousand different users - up to 28,000 a day open 200 thousand pages), a lot of disk space and a lot of security issues etc.
I'm planning now with this new programming capacity to introduce a possibility that one can pay for instance $ 12.50 to get about 12 pages of schematics or a combination of 60 collector prices. Those credits will stay for one year or 6 months. This will hopefully help to keep the organization running when I personally can't go on.
Here you find some facts about Radiomuseum.org: http://antiqueradios.com/forums/viewtopic.php?f=2&t=145099