The sentence you quote is actually meant to -technically- establish a basis for what it means for somebody to run/offer TimescaleDB as part of a value added service (very much allowed) versus a company like AWS offering TimescaleDB purely as a DBaaS offering (not allowed).
There are many, many thousands of companies that use or embed TimescaleDB as part of their service or product offerings, serving huge numbers of customers. We're extremely supportive of their ability to do so. We have no "enterprise features" that are excluded or held back only to paid users.
What we aren't supportive of is AWS running "TimescaleDB-as-a-Service" as part of AWS RDS. Because we know they do that!
The clause you are quoting helps define some of the legal nuances how we get there, ideally in ways that an engineer would understand. In particular, what it means to be a value added service/product versus just "TimescaleDB-as-a-Service".
The alternative legal formulations of this can be found in, e.g.
- Confluent Community License ("Licensee is not granted the right to, and Licensee shall not, exercise the License for an Excluded Purpose. For purposes of this Agreement, “Excluded Purpose” means making available any software-as-a-service, platform-as-a-service, infrastructure-as-a-service or other similar online service that competes with Confluent products or services that provide the Software.")
- Polyform "Shield" License ("Any purpose is a permitted purpose, except for providing any product that competes with the software or any product the licensor or any of its affiliates provides using the software.") https://polyformproject.org/licenses/shield/1.0.0/
These are all getting to similar places, but just putting more emphasis of the legal definition of "competition", which we thought would frustrate engineers with its vagueness.
That restriction makes the license not Open Source. Open Source licenses MUST allow anyone to run the software, for any reason, by definition. Even "as-a-Service". It's a perfectly fine restriction to have, but it shouldn't be called an Open Source license.
(Timescale engineer here)
While AGPL is a value-add for many, TSL isn't as ambiguous in some regards and provides a lot of nice "we won't sue you for this" clauses for users. Clear communication regarding its FOSS status will only help!
That's why Open Source came up in the first place - pointing out that one of the basic reasons for the Timescale license to exist in the first place is to restrict one of the major reasons Open Source licenses exist.
There were also no claims about whatever definition of restrictive you were using. It was just a short statement that the Timescale license was designed to be less restrictive than the AGPL. You can't really be that surprised when somebody comes along and starts judging it by Open Source standards after that, can you?
Comparisons to Open Source and discussions of the pros and cons of both approaches are, of course, fair.
I think Timescale employees should remember to preface "This is our belief on the definition of restrictive" when describing the license as more open than open source licenses, given much of the community might disagree (sometimes vehemently) about that take.
Incidentally, that clause exists as a clear line for value added products and services. Some companies have a restriction that says, "You can't compete with us." That approach struck us as arbitrarily blurry. We took a clear approach that says DML (inserting, querying data) is permitted, but not DDL (creating tables). Again, this is to clearly restrict TimescaleDB-aaS providers and not other companies building true value added products / services on top (e.g., IoT platforms, SaaS companies).
Timescale license does not provide that, so obviously it's more restrictive than even the most viral of open source licences.
To be specific, the sentence "the customer is prohibited, either contractually or technically, from defining, redefining, or modifying the database schema or other structural aspects of database objects," spits in the face of all the ideals of open source. I can respect your decision to choose such a license, there are understandable practical arguments for that, but I can't respect you calling that open source - if you consider that users should be restricted with what they can do with their data schemas, if you include an explicit anti-user-freedom clause, legally mandating software developers to be hostile to their own users - then at least have the guts to openly say that you are against open source (because of all the valid reasons you have, I'm not denying that, you don't have a duty to be pro-open-source), instead of misleadingly labeling your license as such.