HumHub's Community Edition is open-source and self-hosted without per-user software fees; hosting, maintenance, and optional commercial modules or Professional Edition still cost money. Slack publishes Free, Pro, and Business+ pricing, while Enterprise+ pricing is sales-led.

Source: HumHub: platform overview · HumHub license · HumHub editions · Slack pricing

HumHub organizes an internal network into Spaces with their own members, permissions, streams, and enabled modules; optional modules add wikis, calendars, polls, files, and other durable content. Slack centers communication on channels, messages, canvases, and threads. The products overlap, but HumHub is closer to a social intranet than a direct chat-only substitute.

Source: HumHub: Spaces, streams, and modules · HumHub Marketplace · Slack: channels · Slack: canvases

HumHub documents customer-operated installation and also offers managed hosting. Slack's standard service is vendor-hosted and its documentation does not provide a customer-operated Slack server.

Source: HumHub: installation · HumHub: managed hosting · Slack security overview

A self-hosted HumHub operator chooses the server, database, storage, and backup controls. Slack provides workspace export tools whose availability and scope depend on plan, role, approvals, and retention policy. Self-hosting improves control but does not by itself guarantee regulatory compliance.

Source: HumHub: requirements and operator responsibilities · HumHub: backups · Slack: export workspace data

HumHub supports custom themes, configuration, source modification, and modules that can operate globally or within individual Spaces. Slack is proprietary but supports themes, apps, workflows, and platform APIs; its source and core interface are not customer-modifiable.

Source: HumHub: themes · HumHub: module development · Slack platform overview · Slack Workflow Builder

HumHub offers official, partner, community, and paid modules through its Marketplace, plus a REST API module currently labeled beta. Slack distributes a substantially broader catalog of apps and provides mature platform APIs.

Source: HumHub: modules and Marketplace · HumHub REST API module · Slack Marketplace · Slack API

HumHub describes its interface as suitable for nontechnical users, but a self-hosted deployment still needs an administrator familiar with web-server maintenance. Slack provides vendor-managed onboarding across desktop and mobile. The relative UX scores remain editorial and should be supported by an internal usability test.

Source: HumHub: benefits and requirements · Slack: getting started · Slack: mobile apps

HumHub supports public or private Spaces, user roles, invitations, and limited guest access within a specific HumHub network. Slack Connect is designed for shared channels and direct messages across separately administered organizations, giving Slack the stronger packaged cross-company workflow.

Source: HumHub: Spaces and current limitations · HumHub: permissions · Slack Connect overview