We hear this all the time. Customers want to move away from Notes and Domino, but they don’t want to replace Notes with another proprietary platform. They want to use what they have, or what they can get for free.
Notes is a powerful platform. Most companies do not have one or two custom applications, often they have dozens, sometimes hundreds or even thousands.
You could re-write them with something like .Net, PhP or Java and use Microsoft SQL Server (which many have) or MySQL (which is free) on the back end but that would take decades or a small army to pull off, or both. It is more than just development effort. Notes had some unique design constructs that do not easily translate to the relational world. Response documents. Embedded views. Private on first use folders. Access controlled sections. There is a good chance customers are going to have to do a certain level of process re-engineering to make allowance for things the new application has to do differently, or cannot do at all. This means rounding up users and going through a series of workshops. That takes time. If you have hundreds of apps, a lot of time.
If you have many apps you need to automate the migration process. You need to build migration tools, ideally for the design elements, the data, and the security. They do not have to be perfect, there is always going to be some level of manual work required, but you need something that will do that heavy lifting.
You need more than just the applications at the end of the day. You need a way to manage them. You are going to have to build some type of admin tool, perhaps wire up a federated search engine, and build a portal to house the applications. If your company is international you are going to have to provide multilingual capability, and a way to share information with external customers and partners.
Notes never would have taken off if C++ was the development environment, so you would be wise to build some kind of low code designer tool so it is easy to maintain the migrated apps and build new ones.
In the end, if you go the re-write route, you are not buying a platform, you are building one. Then, when you are done (you never will be), you have to maintain it, as operating systems, browsers and data base technology changes. You will be doing what the DOCOVA team has been doing for more than a decade.
If you want to move your applications off Notes and Domino there are two ways of getting there. You can leverage work done by others or you can do it yourself. You can buy a plane ticket or build the airplane. Both will get you there. Keep in mind that the first plane off the assembly line is seldom the best.