The post title in its original context is clearly referring to the confusion discussed in the very first sentence: "Today a page about the new Common Clause license in the Redis Labs web site was interpreted as if Redis itself switched license." The title is saying that Redis core's license was not switched to Common Clause at that time in 2018. That's all. It is not titled "I promise that Redis will remain open source forever".
> This is not the case, Redis is, and will remain, BSD licensed.
True, he doesn't explicitly say for how long, but I don't think it is unreasonable to read "will remain" as "will remain indefinitely" and not as "will remain so until we change our minds".
> I don't think it is unreasonable to read "will remain" as "will remain indefinitely"
That's a reasonable interpretation. But it involves an assumption on behalf of the reader, of words that are not there. I think it's a stretch to consider that specific post a "literal promise" by Antirez.
That said, I just did more research and must admit I am completely wrong with regards to the bigger picture there. My genuine apologies. In the HN commentary on that same post [1], the cofounder/CTO of Redis Labs (Yiftach) apparently made a much more direct statement that "Redis remains and always will remain, open source, BSD license". Due to use of the word "always", that I think can unambiguously be called a literal promise that was broken by the Redis company.
People sometimes change their mind about decisions over time. That isn't the same thing as breaking a promise. You can infer a promise from any declarative statement, but that doesn't mean your inference is correct.
The post title in its original context is clearly referring to the confusion discussed in the very first sentence: "Today a page about the new Common Clause license in the Redis Labs web site was interpreted as if Redis itself switched license." The title is saying that Redis core's license was not switched to Common Clause at that time in 2018. That's all. It is not titled "I promise that Redis will remain open source forever".