Credit is not required, but appreciated :)
All freebies feature an on-page indication whether they are free for personal & commercial, or just personal use.
This is the breakdown between the two licenses:
Personal & Commercial Use
Freebies that are available for personal & commercial use are free for unlimited use in personal and commercial projects. The only limitations of this license includes redistribution in any way, theft & reproduction or use pornographic, fraudulent, obscene, immoral, infringing, illegal, blasphemous or defamatory material.
Freebies available for personal use are limited to projects that will not be related with any business or monetary gain. This includes work for personal art, gifts and other non commercial projects.
PLEASE CONTACT OCDCO FOR AN EXTENDED COMMERCIAL USE LICENSE
Unlimited personal projects
Creating artwork for clothing, packaging, posters or similar commercial products, for sale or for promotional use by you, your company, or your clients (Less than 25,000 units)
Creating branding elements including logos for you or your clients
Creating design works & rasterized images for web use
Embedding products in electronic devices/operating systems/game consoles, etc.
Embedding products in applications
Converting format of product for use on the web.
Any large volume use which includes products, packaging, advertisements, etc. with over 25,000 reproductions
Creating letterform/alphabet products for resale or distribution
Creating personalized products for resale including Print on Demand style business use.
Using products in any broadcast including cinema