Atlas is an "enterprise" GIS System
Along with its analysis and content, Atlas is a "System". It has environments for GIS analysis, resources, and viewing.
The CAPABILITY of Atlas lies in the quality of the Atlas System.
Capability Projects are focused on the strategies, designs, and implementation of the Atlas System.
The Atlas Customers include residents, communities, non-profits, and public agencies, where value is GIS stimulating participation.
These Customers appear to share important requirements for 1) high privacy, and 2) low cost.
It's assumed customers would respond well to "crowd sourcing" capabilities.
The Atlas Customers also include the students who work with the program.
The relationship Atlas has with students is focused on enhancing their educational experience while reducing the cost of that education.
The value proposition with students sets the focus on creating projects that provide students opportunities to enhance market-relevant GIS System management skills.
ESRI (Environmental Systems Research Institute) is the world leader in GIS applications and is the option of choice for many organizations, certainly including government jurisdictions.
As with any commercial operation, ESRI chooses to price itself out of some markets.
Atlas, with its focus on non-profit, community, and GIS students, is one of those efforts that can't afford ESRI product.
Atlas has access to some of the ESRI products via the GIS students it works with. These students are provided tools by ESRI. Atlas also can use individual ArcMap Desktop licenses as long as the individuals with those licenses are volunteers to the 501c3.
The net is that Atlas needs to be in the Open Source space.
The good news is that the open source world for spatial technologies is robust. One indicator is the existance of an international standards organization (similar to W3 for HTML, etc.).
Student Lorn Fant did the intial exploration of qGIS.
His general conclusions were that the product is viable. No investigation of uDig has been done yet.
MapServer makes it clear they are not intending to be a fully-functional web service.
GeoServer focuses on complance/implementaton of OSGeo "standards".
GeoServer makes use of Freemarker, a template engine, at points where developer customizations are allowed.
Templates use Data Models as input. GeoServer has 5 Data Models.
Data Models are a sort of tree of hierarchy where each Element has a Name and a Value. [Same approach used by JSON]
In GeoServer, the Values are Types. Along with basic Types (e.g. boolean, string), there are list, map, and listMap Types.
There are a number of configurations that can be used to deliver GIS services and maps. Discovering and implementing those configurations is part of the learning journey for students.
Other configurations of interest are delivered via an online map service (e.g. Mapbox, ESRI Online) or with a GIS server in the configuration.
Atlas is designed as an open system because it offers the greatest opportunity for student benefit. Because of privacy and cost requirements, it does not include the use of proprietary web map services (e.g. Google Maps, ESRI Online).
Also part of the initial approach is investigating geospatial PDF capabilities. Although geospatial PDFs may not be a long-term direction, it appears it has capabilities that would be a valuable interactive environment for users.
GIS for Server is intended to be part of the overall architecture.
The approach is intended to create an environment for students to provide GIS system management services.
Immense thanks to Brandon for how generously he shares his world, including a great number of the links that started this list