It's your Usenet provider that has download limits -- daily Meg/Gig,
weekly, etc., etc. -- not the software, unless by chance your provider
has their own proprietary downloader / and/or manage their own Usenet
download service.
Here's an excellent site with all about Usenet newsreaders:
http://www.binaries4all.com/
Also definitely see this page, which has a very good comparison of
basic & advanced features of several freeware and shareware Usenet
binaries downloaders:
http://www.binaries4all.com/newsreaders/overview.html
http://www.binaries4all.com/