Assumed audience: People interested in the legal side of open source software.
Over the past few years, I have gradually started using the Blue Oak Model License for all new open source projects. Historically, I had always used the widespread MIT License. Since finding the Blue Oak license, though, I have come to very much prefer it, because it uses clearer language, skips the completely-unnecessary ALL CAPS in favor of using semantic markup (in Markdown or HTML), and comes with a patent license/waiver. In other words, it is similar in guarantees to the BSD 2-Clause Plus Patent license, but it is significantly easier to read.
The whole text of the license (click to expand):
Blue Oak Model License
Version 1.0.0
Purpose
This license gives everyone as much permission to work with this software as possible, while protecting contributors from liability.
Acceptance
In order to receive this license, you must agree to its rules. The rules of this license are both obligations under that agreement and conditions to your license. You must not do anything with this software that triggers a rule that you cannot or will not follow.
Copyright
Each contributor licenses you to do everything with this software that would otherwise infringe that contributor’s copyright in it.
Notices
You must ensure that everyone who gets a copy of any part of this software from you, with or without changes, also gets the text of this license or a link to https://blueoakcouncil.org/license/1.0.0.
Excuse
If anyone notifies you in writing that you have not complied with Notices, you can keep your license by taking all practical steps to comply within 30 days after the notice. If you do not do so, your license ends immediately.
Patent
Each contributor licenses you to do everything with this software that would otherwise infringe any patent claims they can license or become able to license.
Reliability
No contributor can revoke this license.
No Liability
As far as the law allows, this software comes as is, without any warranty or condition, and no contributor will be liable to anyone for any damages related to this software or this license, under any kind of legal claim.
The Blue Oak Model license is from the Blue Oak Council, which is an effort from, among others, Kyle Mitchell. The Council is an effort to publish educational materials as well as useful licenses for folks without super deep pockets to hire lawyers to wrangle all of that. Mitchell himself is well worth reading on software legal issues, and while I do not always agree with his social takes, his legal input on software licensing has been very informative and indeed formative for me over the past few years!
If you are looking for a permissive, non-viral license for your next open source project, I suggest seriously considering the Blue Oak Model license!