Yes, WibTeX is Freeware. No nag screens, time-outs or alike. However, the freeware version is limited to 30 records. If you need more quotations within one database, you should register. See the details in the 'registration' links on these pages.

Hint: To work with more than 30 records without registration, you may also save the data in different BibTeX files and merge the files in a text editor (like Notepad). Word lists of references can also be merged within Word, for example. However, if you want to use search functions, like to have a full overview etc. then it is surely more convenient to register - it's not that expensive after all!