When creating a new project today, am I allowed to license my software using the older version of licenses such as GPLv2 (vs. GPLv3), or BSD 4 clause (vs BSD 3 clause).ORAm I only allowed to use the latest version of these licenses instead?
Using older versions of licenses in new projects
licensing;license recommendation
You can use any version of any license you please.  You are the author. You do what you want.No FOSS license could say something to the contrary, including no such license could restrict you to use other licenses or other version of a license for your original work .Practically each new version of common FOSS licenses is in itself a new license. Most versioned licenses have terms that may allow to use a newer version of a license for code using a previous version, but not always. This is a permission in all cases, never a restriction.In some cases such as the GPL family the relationships between all these versions can start being .... it's complicated!.