In the article they describe how they are running the proprietary memory training software on the M4 core in the i.MX 8 chip.

Running proprietary code on the i.MX 8 chip means that it is not 100% running on free software.

The large backlog of orders is a big red flag for the product to investors. I don't think continuing to take money is as big of a signal. Having a big backlog means that competitors who can actually deliver a product are going to be making more sales. It's a giant competitive advantage to be able to buy a phone and receive it in a couple days compared to buying a phone and receiving it in a couple years. For the fast moving technology space of phones with every year phones get delayed the product's hardware will become more and more outdated making the competitors look better.

To me keeping the orders, doubling the price, and trying not to give out refunds makes me think Purism has serious money issues.