What I can say is that I can cover costs out of pocket every month indefinitely (because each user covers their telco costs of that line, I'm just covering infrastructure) and my hosting fees are easy to cover even if we have no users.
We're probably not a typical startup in that sense. We have sustainability and independence in mind. At this point the only thing investors could offer us is the ability to grow faster. An important thing, but I like giving stability its own rights, too.
Also self sufficiency and independence are great for a startup, but that doesn't guarantee that your company will continue to exist. Are you setting this up as your main source of income? Does it pay your bills? Will you get bored of it in 6 months? These are all questions that are going through my mind. Your FAQ doesn't answer them. Your terms of service don't address them and literally guarantee nothing: "We do not guarantee any level of service at the time of this writing. This will change when we have a significant track record with which to stand claims against. In practice we meet high standards, but will not be held to those standards." That makes me very hesitant to not only pay you $15 per month but more crucially entrust you with one of the most important ways people contact me.
In the absence of Google Voice, this service might be interesting; however, otherwise, why would I pay 15*12 = 180 USD/year for something that I can already get for free?
https://www.washingtonpost.com/blogs/the-switch/wp/2015/07/0...
Google Fi looks interesting but it appears it will work via your cell phone rather than PC and/or land line (via, for example, Obihai's Obi200 and ObiTalk ... very highly recommended for GV as it is now). And there's Google Fi's price of $30 per month.
Any thoughts on going open source?
Please pardon me for saying so, but it seems like you do care about open source, or at least leveraging it to save your business money.
You are correct that I do care about open source. I don't have much of a care about going open source for our stuff. We make our money on service, not software, but I can see the appeal. Essentially I'm just "meh" about doing it myself here.
It should be noted I love the freeswitch folks and while I'm not involved in writing the C (that takes me back), I hang out in the IRC channel and help there when able. I've looked at the code (it's hard to use binaries with FS), but never had to submit a patch as of yet. They're rock solid and deserve every support contract the get!
Go ClueCon!
It's rough but worked reliably.
[1] asterisk/freeswitch, cloudy telco api, custom software with myriad options for receiving and placing calls.