It's not an OSI endorsed license. Elastic insists on copyright transfers for any code contributions as well, so that makes contributing under a different license not possible (their choice).
Crate is upset because they've created a significant derivative work which complicates their business under the new license. Apache 2.0 is intentionally designed to support this kind of thing; which is why it is a popular license for companies working together on OSS projects.
Copyright transfers like Elastic is practicing are of course a big risk for such companies. IMHO, any such projects has long term challenges. Most long lived OSS projects have a multitude of copyright holders. E.g. re-licensing Linux would be very impractical as it as many thousands of contributors some of whom have passed away (i.e. their families inherited the copyright). That's a strength of that project; it's forever stuck on GPL2, which provides enough wiggle room that the likes of Google, Samsung, and many others can use it to create software for their products.
Amazon's work is of course less significant but this license is designed to prevent derivative works from being likely to succeed commercially. Even Amazon's use which technically did not involve actually modifying the source code (not a single line, they used a binary OSS release provided by Elastic and added plugins) would be illegal under this license. That's not open; sorry.
Crate is upset because they've created a significant derivative work which complicates their business under the new license. Apache 2.0 is intentionally designed to support this kind of thing; which is why it is a popular license for companies working together on OSS projects.
Copyright transfers like Elastic is practicing are of course a big risk for such companies. IMHO, any such projects has long term challenges. Most long lived OSS projects have a multitude of copyright holders. E.g. re-licensing Linux would be very impractical as it as many thousands of contributors some of whom have passed away (i.e. their families inherited the copyright). That's a strength of that project; it's forever stuck on GPL2, which provides enough wiggle room that the likes of Google, Samsung, and many others can use it to create software for their products.
Amazon's work is of course less significant but this license is designed to prevent derivative works from being likely to succeed commercially. Even Amazon's use which technically did not involve actually modifying the source code (not a single line, they used a binary OSS release provided by Elastic and added plugins) would be illegal under this license. That's not open; sorry.