What host/slicer programs that are open source and user friendly would people recommend? Seems that Cura 2.X will not work with smoothieware for the foreseeable future 
We need to get some cool developers to work on LaserWeb4 support for 3DP 
Seconding @Ariel_Yahni_UniKpty .
Right now old Cura, Pronterface, S3D, and Octoprint are the list.
I find old Cura to be limiting but it does work, Pronterface is ugly S3D is expensive, and I love Octoprint but I still slice elsewhere.
MatterControl is open source. “User friendly” is subjective – I didn’t find it too confusing when I started using it, and I’m not a super genius.
The old Cura is still my go-to, but there are a lot of ways in which MatterControl is more user-friendly (unfortunately, most of them are ways that just tend to get in my way). I don’t find s3d to be particularly simple or user-friendly, and really only use it if I need the manual supports feature.
Old cura is a terrible host program, but I really like it as a slicer. My workflow is to bring an STL in, arrange if necessary, save it to an SD card and name the file auto0.g. Then I just plug that into the printer and hit reset. No host programs required. On the rare occasion that I actually do need manual controls, I use gcodeprintr more than anything else. Pronterface is probably second, but I haven’t had a use to run a print directly over USB in several years. I guess the last thing I used for that regularly was Repetier Host, but like Cura, the old versions of that were better than the more recent ones.
Prusa version of slic3r is good. Smoothie support as well.
Thanks for the suggestons. We’re looking to find a software that we can package with our printer to new users who aren’t familiar with 3D printers. Which is why Cura 2 was our choice, because it’s user-friendly. Seems like the free, open-source solutions are becoming more and more limited these days.
@Shai_Schechter definitely suggest Slic3r Prusa Edition. It’s open source and is user friendly, while still having the option to switch to an “expert mode.”
Try CraftWare - free and with custom supports feature like S3D
Is it that difficult to adopt Cura2 to smoothieware?
No love for slic3r? That’s the best, imho. It is reliable, works, and is awesome! The prusa version is even better and you can adjust it for your printer!
For Deltas, the print recovery feature in MatterControl is pretty awesome. Definitely worth checking out
I second @Whosa_whatsis , I am printing directly from the printers themselves via the SD card. I do not trust USB live printing a lot, especially with a full featured/bloated OS behind, unless I am debugging or calibrating a new printer (in which case I mostly use pronterface command line, and its convenient programmable macro buttons).
I also slice with an older version of Cura, and to be frank I fear a bit if/how Ultimaker will support “competing” printers in the future.
Slic3r is my second choice, as it has some features I would not like to see traded off with too much “user friendliness” which seems to be the trend nowadays. It handles printers and materials in a sane way imho.
As far as purely just the host functionality, from what I’ve used Simplify3D has been a breeze, couldn’t ask for much more (it costs $ though, of course). Octoprint also works great in that regard too.